Demi Lovato seems to have relit the spark with her on-again, off-again boyfriend Wilmer Valderrama. The former “That ’70s Show” star, 32, joined Lovato, 20, during a private event at Bagatelle LA on Wednesday night in West Hollywood to celebrate the Season 2 premiere of “The X Factor.” “Wilmer stayed by Demi’s side all night,” says a spy. “He was very protective of her and had his legs straddled around her chair while they watched the show.” Lovato and Valderrama were seen having dinner together earlier this month. The duo first started dating in 2010 and briefly reunited in 2011 after Lovato was released from a treatment center for an eating disorder and cutting. The couple has always remained low-key, most likely due to their 12-year difference, which sources tell us is a concern for Lovato’s family. Lovato recently shot down rumors she was dating One Direction’s Niall Horan after they were spotted dining together after the 2012 MTV Video Music Awards. Her rep declined to comment.